Dysfunction of the WW domain-containing adaptor with coiled-coil, WAC, gene underlies a rare autosomal dominant disorder, DeSanto–Shinawi syndrome (DESSH). DESSH is associated with facial dysmorphia, hypotonia, and cognitive alterations, including attention deficit hyperactivity disorder and autism. How the WAC protein localizes and functions in neural cells is critical to understanding its role during development. To understand the genotype–phenotype role of WAC, we developed a knowledgebase of WAC expression, evolution, human genomics, and structural/motif analysis combined with human protein domain deletions to assess how conserved domains guide cellular distribution. Then, we assessed localization in a cell type implicated in DESSH, cortical GABAergic neurons. WAC contains conserved charged amino acids, phosphorylation signals, and enriched nuclear motifs, suggesting a role in cellular signaling and gene transcription. Human DESSH variants are found within these regions. We also discovered and tested a nuclear localization domain that impacts the cellular distribution of the protein. These data provide new insights into the potential roles of this critical developmental gene, establishing a platform to assess further translational studies, including the screening of missense genetic variants in WAC. Moreover, these studies are essential for understanding the role of human WAC variants in more diverse neurological phenotypes, including autism spectrum disorder.

Summary: Neurofibromatosis-1 (NF-1) is a monogenic disorder caused by mutations in the NF1 gene, which encodes the protein, Neurofibromin, an inhibitor of Ras GTPase activity. While NF-1 is often characterized by café-au-lait skin spots and benign tumors, the mechanisms underlying cognitive changes in NF-1 are poorly understood. Cortical GABAergic interneurons (CINs) are implicated in NF-1 pathology but cellular and molecular changes to CINs are poorly understood. We deleted Nf1 from the medial ganglionic eminence (MGE), which gives rise to both oligodendrocytes and CINs that express somatostatin and parvalbumin. Loss of Nf1 led to a persistence of immature oligodendrocytes that prevented later born oligodendrocytes from occupying the cortex. Moreover, PV+ CINs were uniquely lost, without changes in SST+ CINs. We discovered that loss of Nf1 results in a graded decrease in Lhx6 expression, the transcription factor necessary to establish SST+ and PV+ CINs, revealing a mechanism whereby Nf1 regulates a critical CIN developmental milestone.

Dysfunction of the WW domain-containing adaptor with coiled-coil, WAC, gene underlies a rare autosomal dominant disorder, DeSanto-Shinawi syndrome (DESSH). DESSH is associated with facial dysmorphia, hypotonia, and cognitive alterations, including attention deficit hyperactivity disorder and autism. How the WAC protein localizes and functions in neural cells is critical to understanding its role during development. To understand the genotype-phenotype role of WAC, we developed a knowledgebase of WAC expression, evolution, human genomics, and structural/motif analysis combined with human protein domain deletions to assess how conserved domains guide cellular distribution. Then assessed in a cell type implicated in DESSH, cortical GABAergic neurons. WAC contains conserved charged amino acids, phosphorylation signals, and enriched nuclear motifs, suggesting a role in cellular signaling and gene transcription. Human DESSH variants are found within these regions. We also discovered and tested a nuclear localaization domain that impacts the cellular distribution of the protein. These data provide new insights into the potential roles of this critical developmental gene, establishing a platform to assess further translational studies, including the screening of missense genetic variants in WAC. Moreover, these studies are essential for understanding the role of human WAC variants in more diverse neurological phenotypes, including autism spectrum disorder.

Tuberous Sclerosis Complex is a complex syndrome that affects multiple organs and is caused by dysfunction of either the TSC1 or TSC2 genes. One of the least understood features of TSC is the impact of TSC1&2 variants on brain phenotypes, including elevated rates of autism spectrum disorder and seizures. Moreover, while a great deal of work has uncovered how loss of either gene can alter various neural cell types, the impact of many variants in TSC and on these cell types is poorly understood. In particular, missense variants that cause minor changes in the proteins are expected to cause functional changes that differ from a complete loss of the protein. Herein, we examined how some missense variants in TSC1 impacted the development of cortical inhibitory interneurons, a cell type whose molecular, cellular and physiological properties are known to be altered after loss of mouse Tsc1 . Importantly, we found that most missense variants complemented phenotypes caused by loss of Tsc1 and resulting in elevated MTOR activity as well as several cell intrinsic physiological properties. However, distinct variants showed deficits in complementing an increase in parvalbumin levels, which is observed after loss of Tsc1 and demonstrated smaller amplitudes of after hyperpolarizations. These data suggest subtle but sensitive phenotypes can be detected by some TSC1 missense variants and provide an in vivo system in which to better assess TSC variants.